The present disclosure relates to gas turbine engines, and more particularly to a nacelle therefor.
In a subsonic aircraft having an externally mounted engine, for example, a turbofan engine mounted by a pylon, aerodynamic drag due to freestream airflow over the nacelle of the engine may cost approximately 4% of the total engine thrust output.
One conventional technique to reduce fan nacelle drag is to provide a relatively thick nacelle inlet so that airflow will flow around and not separate from the outer or inner surface of the fan nacelle. Since many turbofan engines provide a fan of significant diameter, a fan nacelle therefor will necessarily be of a significant diameter. This may substantially increase fan nacelle size and weight so that any reduction in the fan nacelle thickness and length in front of the fan section competes against the desire to maintain attached flow.